(A) Field of the Invention
The present invention relates to a power transmitting mechanism that disconnects power transmission from a first rotor to a second rotor when an excessive torque (load) is transmitted between the first rotor and the second rotor.
(B) Description of the Related Art
Japanese Unexamined Patent Publication No. 11-30244 discloses such a power transmitting mechanism, which has a rotor driven by an external drive source and a rotor for a device. The rotors are coupled to each other by a rubber part for transmitting power. When the transmission torque from the external drive source to the device is excessive due to a malfunction of the device, or when the device is locked, the rubber part breaks. Thus, power transmission from one of the rotors to the other is disconnected. Accordingly, the mechanism prevents the external drive source from being affected by an excessive transmission torque.
According to the above prior art, even though the rubber part broken out due to the excessive torque, the external drive source and the device are partially engaged by friction at the location of the rubber part. Thus, power transmission between the rotors is not completely disconnected. This results in poor fuel economy when, for example, the external drive source is an engine of a vehicle and the device is a vehicle auxiliary device.
Accordingly, it is an objective of the present invention to provide a power transmitting mechanism that reliably disconnects power transmission between a first rotor and a second rotor when the transmission torque between the rotors is excessive.
To achieve the foregoing objective, the present invention provides a power transmitting mechanism comprising a first rotor, a second rotor, and a coupler. The second rotor is coaxial to the first rotor and is driven by the first rotor. The coupler connects the first rotor to the second rotor such that the coupler uncouples when the torque transmitted by the coupler exceeds a predetermined value. The coupler includes a first coupling member and a second coupling member. The first coupling member is formed on the first rotor. The second coupling member is formed on the second rotor. One of the coupling members includes an arm. A distal end of the arm engages the other of the coupling members. The arm is disengaged from the other of the coupling members. The distal end moves in a generally radial direction of the rotors to a non-interfering position when the coupler uncouples.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.